|Debut:||Manga Volume 2, Anime Episode 6|
|Eye Color:||Purple / Violet|
Youji Sagan(瑤二, Yōuji) is the Sacrifice of the Zero (Male) pair. He is one of Nagisa Sagan's experiments, and presumably the second generation of the Zero project . He is the Sacrifice of Natsuo Sagan (who is also a Zero). Youji and Natsuo are infamous for their unwillingness to follow rules as well as their sadistic pleasure in witnessing people struggle and suffer. He makes his first appearance in Volume 2/Episode 6, when he and Natsuo attempt to rape Hitomi Shinonome. Upon nearing their attempt to rape Hitomi, Soubi Agatsuma thwarts their efforts and challenges them to a battle without the company of Ritsuka Aoyagi, his Sacrifice. Despite the pairs demands/recommendations for Soubi to contact his Sacrifice, he stubbornly refuses claiming he could defeat them without his Sacrifice's aid. Youji and Natsuo ultimately corner the now weakened yet unmoved Soubi and start to physically torture him to the point that they nail his hand to the ground in order to persuade him to admit defeat. Upon nearing possible triumph over him, Soubi casts a spell on them which changes the battle areas climate close to Absolute 0 which lowers their body temperatures to almost fatal levels.
Soubi then reveals his knowledge of Youji and Natsuo's defect: Zeros cannot adapt their bodies to cold or hot temperatures as normal humans can. As a result, the Sagans are left with no other option than to forfeit the battle and admit defeat in fear of dying in the harsh climate. When Soubi wins the battle, Natsuo tells him that he and Youji have no place to return to upon losing a battle. Soubi offers to let them live at his apartment with him and the Sagans warily accept, unwilling to return to Nagisa fruitless. Youji and Natsuo promised to care/serve Soubi and Ritsuka; as a result, Soubi does nothing to harm them. Throughout the remainder of the series, Youji and Natsuo take on roles as protagonists who occasionally aid Soubi in various tasks and errands. In chapter 85, Youji and Natsuo become classmates of Ritsuka. They both sit on either side of Ritsuka to share his textbook even though it is difficult for all three of them to see. Yuiko offers Youji to share her textbook but he refuses and insults her by calling her, "fugly".